What would happen if wolves were reintroduced into the Highlands? Well, that depends - are you measuring the impact on sheep or people?

Bringing back wolves after 200 years may seem extreme, but the owners of many Highland estates believe it would help curb a growing nuisance. No, not the ramblers - the red deer.

Now the results of a study by a Norwegian biologist have enhanced their argument.

Dr Erlend Nilsen of the University of Oslo used computerised predator-prey modelling to study how wolves would affect populations of red deer in the Highlands.

He calculated that re-introducing wolves "would reduce deer density by more than 50% in some areas", which he estimated would be profitable for estates. "Land owners would no longer need to conduct expensive and unpopular deer culls, while still being able to retain a trophy hunt," he said.

So far, so good. But what about livestock? Counting sheep was too taxing for Nilsen's computer model, so he conducted a survey of attitudes instead.

"We found that people who live in the Highlands are generally positive to the idea," says Nilsen. "But farmers hold more negative attitudes. A reintroduced wolf population would increase livestock mortality and reduce flock sizes."

In northern Spain, wolves are responsible for 80% of all sheep deaths. But Nilsen argues that losing sheep would be less important to farmers in Scotland because, he says, they make most of their income from subsidies.

His study is published this week in the journal of the Royal Society.

Tasty toxic toads Feed a poisonous toad to a poisonous snake and what do you get? An even more poisonous snake.

It sounds like a bad gag, but in fact this is a remarkable evolutionary phenomenon, discovered this week in Japan. Scientists were curious as to why the tiger water snake, a poisonous grass snake, has such a strong appetite for toxic toads.

It transpired that the toads are tasty because their poison is a useful weapon. When digesting the toads, the snakes harvest their poisons and store them in their own neck glands, allowing them to defend themselves more effectively against predators.

The discovery was made by Deborah Hutchinson from Old Dominion University, Virginia, by studying snakes from two Japanese islands.

On the toad-free island of Kinkazan, she found that the snakes' poison glands completely lacked "bufadienolides". But snakes from Ishima, where toads are plentiful, had high levels of these toxins in their poison glands.

To confirm the link, Hutchinson then fed newborn snakes on either a toad-rich or a toad-free diet. The snakes fed with toads were not only more venomous; they could also arm their offspring with bufadienolides, just like when human mothers pass nutrients to their babies in the womb.

The ability to harvest poison from prey - "toxin sequestration" - is also known in tropical frogs, and one species of Guinean bird, according to her paper. It will be published this week in the journal Proceedings of the National Academy of Sciences.